Tumors are immunogenic and yet, are not rejected. One of the reasons that tumors may survive despite their immunogenicity, is the possibility that specifically sensitized cells cannot migrate to the site of the tumor in sufficient quantity to cause rejection. We have noted that immunity develops in the tumor bearing host but that the cells do not migrate to the graft before suppressor cells also developed to turn off the immune response. We are now trying to determine the characteristics of cells which migrate to allografts in order to determine the critical differences between immunogenic allograft and the immunogenic tumor graft. In the coming year we plan to use tumors within the sponge matrix graft rejection model and compare the cells which infiltrate the tumor graft with the cells which we have characterized already which infiltrate the allograft.